Ok, I got it. The only standard command that comes halfway close to 'Tail Hook up/down' is
'Heck nach oben/unten' (rather meaning tail up/down). Well, I assigned a key combination to it and it did the job!! Guess that it must have been way past midnight and after a couple of beers when it came to translating that one...

Anyway, it works great now and I take the opportunity to thank you for doing such a great job in both the TLK39 and the MIG! Just keep them coming.
Cheers,
Joerg